THE PROBLEM OF FOOD 9 



been brought to show that it is a toxic substance, 

 notwithstanding the nonsense published in certain 

 advertisements. 



" Heat-giving" Food. This name is also used in 

 consequence of a misunderstanding of fundamental 

 facts. Properly speaking, it is applicable to all kinds 

 of food, and is equivalent to energy-giving. The 

 confusion is due to the failure to realize that heat is 

 one of the forms of energy, which are mutually con- 

 vertible. It is incorrect to speak of "heat and 

 energy" as is often done. If a food is capable of 

 affording heat, it is also capable of giving the other 

 kinds of energy also, including that of muscular 

 work. Sugar is sometimes called a heat-giving sub- 

 stance, whereas it is the typical source of energy for 

 muscular contraction. If any food is to be called 

 specially heat-giving, alcohol, according to E. Mel- 

 lanby's investigations, might perhaps be more ap- 

 propriately called by this name. Protein, in the par- 

 ticular aspect to be referred to below, might also be 

 included. 



Before we pass to this latter point, a word may be 

 said about Clothing. Part of our food is spent in 

 keeping up our temperature, mainly as a by-product 

 of muscular work, and especially in cold weather. It 

 is clear, therefore, that the less heat is lost to the out- 

 side the less food is needed. Hence a certain economy 

 is effected by warm clothing, and, it may be added, 

 bv warming the house. 



* o 



It is necessary to be cautious in making definite 

 assertions as to any special value of protein food. 

 Some hold that a full protein diet ensures greater 

 resistance to infection. I confess that I have been 

 unable to find any satisfactory evidence that this is 

 the case. Dr. Carter, of Birmingham, in a careful 

 investigation, found no evidence that the incidence of 



